avoid showing mkdir error which happens when rebuilding

--- "archlinux version!_dkms-2.2.0.3-15-any/dkms"	2014-11-05 11:51:54.000000000 +0100
+++ "manjaro(archlinux based) version patched_dkms-2.2.0.3-15-any/dkms"	2014-11-05 12:06:26.342732248 +0100
@@ -1245,5 +1245,5 @@ do_build()
 
     # Save a copy of the new module
-    mkdir "$base_dir/module" >/dev/null
+    mkdir "$base_dir/module" >/dev/null 2>&1
     for ((count=0; count < ${#built_module_name[@]}; count++)); do
 	[[ ${strip[$count]} != no ]] && strip -g "$dkms_tree/$module/$module_version/build/${built_module_location[$count]}${built_module_name[$count]}$module_suffix"
